Electrically controlled refrigerant charging device



Sept. 10, 1968 R. A. JOHNSON ET AL ELECTRICALLY CONTROLLED REFRIGERANT CHARGING DEVICE Filed Feb. 15, 1967 2 Sheets-Sheet 1 52 so; ,45 43 I INTERLOCK CONTROL CIRCUIT CIRCUIT 32 ,0 PRESSURE 34 PRESSURE TRANSDUCER TRANSDUCER I 33 I t 6 n-M f [3 BLEED VALVE 1 ll LINLE'I VALVE CHARGE BOTTLE I BOLJ F 24 2a 22 42 L I" L -L[L] -(L D L SUCTION LINE (ct :C"'- .E -C" C 25 VALVE 0R C- l I Cl\ Il?L|"||E:ARY: 2s --J/2e wnmzssss: INVENTORS jflq W Richard A. Johnson, William V Miller and Robert A. Essig.

Sept. 10, 1968 R. A. JOHNSON ET AL 3,400,552

ELECTRICALLY CONTROLLED REFRIGERANT CHARGING DEVICE Filed Feb. 13, 1967 2 Sheets-Sheet 2 United States Patent 3,400,552 ELECTRICALLY CONTROLLED REFRIGERANT CHARGING DEVICE Richard A. Johnson, Monroeville, Pa., and William V.

Miller, Novelty, and Robert A. Essig, Elyria, Ohio, assignors to Luxaire, Inc., Elyria, Ohio, a corporation of Delaware Filed Feb. 13, 1967, Ser. No. 615,742 9 Claims. (Cl. 62149) ABSTRACT OF THE DISCLOSURE Electrically controlled inlet and bleed valves are detachably connected to the suction line of an operating refrigeration system and to a source of refrigerant. Pressure and temperature transducers sense the ambient temperature, liquid line pressure, suction line temperature and suction line pressure to open the inlet valve to add refrigerant or to open the bleed valve to remove refrigerant from the operating refrigerating system. Certain relations of ambient temperature and suction line pressure will prevent the inlet valve from opening even though related suction line temperature and pressure is such as to normally open the inlet valve.

Cross references to related applications This application is an improvement for the mechanically controlled and operated refrigerant charging device disclosed and claimed in the copending application Ser. No. 498,923 by Miller and Essig, filed Oct. 20*, 1965, and assigned to the same assignee as the subject invention.

Background of the invention The aforementioned copending patent application is classified in Class 62, refrigeration, and Subclass 149, automatic control for withdrawing and adding refrigerant from or to a normally closed system, and it is believed that the subject patent application and invention pertains to that same field of invention.

Prior to the invention of the aforementioned copending patent application, the most common procedure for charging a refrigeration system was to weigh a predetermined amount of refrigerant for addition to the system after first bleeding the system of any pre-existing charge of refrigerant. Such a procedure is inaccurate in the field, is wasteful, and cannot be accomplished with an operating system. The US. patent to Etherington et al., 2,951,350, issued Sept. 6, 1960, discloses a variable capacity refrigeration system which provides an accumulator to contain an excess charge of refrigerant and the charge of refrigerant in the operating system may be varied by valving refrigerant between the accumulator and the remainder of the system. The system of Patent 2,951,350 may not be used to detachably connect a source of refrigerant to a conventional operating refrigerant system of either the expansion valve or capillary type since there is no provision of any means to control the inlet of refrigerant from a separate source of refrigerant to the system in response to both suction line temperature and pressure as well as liquid line pressure and ambient temperature otherwise referred to as condenser inlet and temperature. The above mentioned copending patent application Ser. No. 498,923, disclosed a charging device having mechanically operated inlet, bleed, and blocking valves with the blocking valve being controlled by ambient temperature and liquid line pressure in an arrangement to prevent charging of the system even though the inlet valve as controlled by suction line pressure and temperature may be open. The arrangement of three mechanically controlled valves is effective but is comparably more bulky and less accurate than the provision of two electrically controlled valves with electrical transducer control systems as provided by the present invention.

Summary of the invention The charging device of the invention includes two electrically controlled valves which may be respectively called inlet and bleed valves adapted to be detachably connected to a suction line gauge port of an operating refrigeration system and to a source of refrigerant. A first pressure transducer and a first temperature transducer are adapted to be connected to the suction line to produce electric signals related to the temperature and pressure of the refrigerant in the suction line and these signals are summed and connected to a control circuit to cause the electric inlet valve to open to pass additional refrigerant into the suction line of the operating system for a predetermined related condition of suction line temperature and pressure. A second pressure transducer is adapted to be connected to the liquid line gauge port of the operating refrigeration system and a second temperature transducer is adapted to respond to the ambient temperature to provide electric control signals to be summed and connected to an interlock circuit that is effective in the circuit to the inlet valve from the inlet control circuit to prevent the electric inlet valve from opening in the presence of predetermined related conditions of liquid line pressure and ambient temperature regardless of the related conditions of suction line pressure and temperature. Additionally the bleed valve is controlled by the control circuit for certain related conditions of pressure and temperature in the suction line to be open to bleed excess refrigerant from the refrigeration system while the inlet valve is closed. Both of the summing circuits for the respective transducers are provided with adjusting devices such as potentiometers to predetermine the desired relations of temperature and pressure for the controlling of the respective inlet and bleed valves.

Brief description of the drawings Further advantages of the invention and features thereof will be apparent with reference to FIGURE 1 of the drawings which discloses a block diagram of the invention as it may be tdetachably connected to an operating refrigeration system of either the expansion valve or capillary tube type and FIGURE 2 of the drawings which is a circuit diagram of one embodiment of electrical control circuit for controlling the electrical inlet and bleed valves.

Description 0 the preferred embodiment of the invention The invention will be first described with reference to the block diagram of FIGURE 1 of the drawings which shows an operating refrigeration system 20 including an evaporator coil 21, a suction line 22, a suction line gauge port 23, a compressor 24, a condensing coil 25, a liquid line 26, a liquid line gauge port 27, and either an expansion valve or a capillary tube 28. The electrically controlled charging device of the invention includes the electrically controlled inlet valve 31 with its operating coil 32 and the electrically controlled bleed valve 33 with its electric operating coil 34. The outlet port of the inlet valve 31 and the inlet port of the bleed valve 33 are adapted to be detachably connected by tubing 35 to the suction line gauge port 23 of the operating refrigeration system 20. The inlet port of the inlet valve 31 is adapted to be connected by tubing 36 to an external source of refrigerant such as the charge bottle 30. The outlet port of the bleed valve 33 is adapted to be open to atmosphere for purposes of discharging excess refrigerant from the suction line gauge port 23 when the bleed valve 33 is open. A first pressure transducer 40 which may be a conventional pressure potentiometer of the Bourdon tube type is also connected by the tubing to be detachably connected to the suction line gauge port 23 to sense the suction line pressure in the operating refrigeration system. An electric temperature transducer 42 is adapted to be clamped to the suction line 22 in any suitable manner to provide an electrical signal related to the suction line temperature. A summing circuit 43 receives the electrical signals from the pressure transducer and the temperature transducer 42 and relates them to a predetermined setting as determined by the manual operated potentiometer 44 to produce a signal to the control circuit 45 which will cause the coil 32 of the inlet valve to be energized to open the inlet valve for predetermined related conditions of suction line pressure and temperature as sensed by the first pressure transducer 40 and the first temperature transducer 42.

Similarly the control circuit 45 is effective to energize the coil 34 of the bleed valve 33 to open the bleed valve for certain predetermined related conditions of suction line pressure and temperature as indicative of an excess of charge in the refrigeration system.

Generally speaking, the system thus far described including the control circuit 45 and the electrically con trolled inlet and bleed valves 32 and 34 respectively is effective to correctly predetermine the charge of refrigerant in an operating refrigeration system of the capillary tube type. However under certain conditions an ambient temperature the related conditions of pressure and temperature in the suction line 22 could be a false indication that the refrigeration system requires additional refrigerant causing the electric inlet valve 31 to be open. In

order to prevent an overcharge of refrigerant under such conditions, the interlock circuit of the invention is provided to be interconnected in the circuit between the control circuit 45 and the inlet valve coil 32 in a manner to disable such connections and prevent the energization of the inlet valve coil 32 by the control circuit 45 when related conditions of ambient temperature and pressure in the liquid line 26 are present.

For this purpose, a second pressure transducer 51 is adapted to be detachably connected by the tubing 52 to the liquid line gauge port 27 of the operating refrigeration system and the electrical signal from the second pressure transducer 51 is connected by the summing circuit 52 to the interlock circuit 50. An ambient temperature sensor 53 producing an electric signal is also connected to the summing circuit 52 and a manually adjusted potentiometer 54 is provided to predetermine a setting of related condition of ambient temperature sensed by the second temperature transducer 53 and liquid line pressure sensed by the second pressure transducer 51 which would be effective to provide an electrical signal to the interlock circuit 50 such as to disable the connections between the control circuit 45 and the inlet valve coil 32 in a manner to prevent the opening of the inlet valve 32. Thus a safety interlock is provided to prevent the overcharging of a capillary tube type of operating refrigeration system in the presence of certain ambient temperature and liquid line pressure conditions.

An additional application of the electrical control charging circuit of the invention is in the charging of an operating refrigeration system of the type using an expansion valve instead of a capillary tube. When charging an expansion valve type of refrigeration system the liquid line pressure as related to ambient temperature are the most reliable determining parameters. Therefore, when charging an operating expansion valve refrigeration system, the manual potentiometer 44 or the summing circuit 43 controlling the inlet valve 31 in response to suction line temperature and pressure parameters may be set to a minimum value so that the inlet valve 31 would be normally open. However the manual control potentiometer 54 for the summing circuit 52 connected to the second pressure transducer 51 that is connected to sense the liquid line pressure at the liquid line gauge port 27 is set at a position which will relate the electrical signals from the second pressure transducer 51 and the second or ambient temperature transducer 53 to cause the interlock circuit 50 to close the previously opened inlet valve 31 when the desired charge is reacheed in the operating refrigeration system. Of course the bleed valve 33 will be effective to be energized to be open to bleed an excess charge of refrigerant from the operating refrigeration system if such is indicated by suction line temperature and pressure parameters.

Referring to FIGURE 2 of the drawings, a brief description of a circuit diagram of one form of electrical control circuit embodying systems previously described in connection with FIGURE 1 of the drawings is disclosed. Since various types of well known electronic logic circuits may be used to provide the block diagram functions of the invention as previously described, a detailed description of the circuit of FIG. 2 is not believed to be required herein. A power supply comprising full wave bridge connected rectifiers is generally shown at and a voltage regulating circuit is generally shown at 101 t provide a source of direct current for energizing the various circuit components such as transistors, transducers, and inlet valve operating coil 32 and the bleed valve operating coil 34. The first pressure transducer is shown as a variable potentiometer 40 adapted to respond to suction line pressure while the first temperature transducer 42 is shown as a thermistor connected in series with the manually adjustable potentiometer 44 providing the control setting for the summing circuit 43 (FIG. 1). The liquid line or second pressure transducer 51 is shown as a variable potentiometer while the ambient or second temperature transducer 53 is shown as a thermistor connected in series with the manually operated potentiometer 54 for determining the setting of the summing circuit 52 (FIG. 1).

Suction line pressure and temperature signals are summed along with a control setting signal from the potentiometer 44 at the bases of transistors 102 and 103. Selection of the proper component values for the resistors 104 and 105 with calibration of the thermistor 42 and potentiometer 54 determines the required control function for a particular refrigerant being used. Transistor pairs 102, 102a, 103, and 103a, along with their subsequent amplifying stages open and close the charge valve 32 and the bleed valve 34 in response to the sensed parameters of suction line pressure and temperature. The base biasing of transistors 102a and 103a provides a desired deadband between the opening of the inlet valve 32 and the opening of the bleed valve 34. Feedback from transistors and 11 provide latching of the inlet valve 32 and the bleed valve 34 and a desired amount of hysteresis between opening and closing of the said inlet and bleed valves.

The high pressure interlock circuit for preventing the operation of the inlet valve 32 to its open condition is controlled at the base of transistor 112 by summed signals from the liquid line pressure potentiometer 51 and ambient temperature thermistor 53 together with the control setting for the potentiometer 54. When the summed control signal from the potentiometer 51 and the thermistor 53 exceeds a predetermined level, transistors 112 and 114 are latched in the conducting state and a gate signal through resistor 115 disables the transistor 110 and prevents the energization of the inlet valve coil 32 for opening the inlet valve. The transistor pairs 112 and 112a are effectively the summing circuit for the signals from the liquid line pressure potentiometer 51 and the ambient temperature transducer or thermistor S3 to control the operation of the interlock circuit including the previously described transistor 114 and the coupling resistor 115. Resistors 120, 121, and 122 are of selected values to obtain the proper control function for a particular refrigerant being used. Since the control functions are determined by the proper selection of values for the resistors 120, 121, 122, 104 and 105, in conjunction with calibration of the temperature sensors and pressure potentiometers, the control system can easily be adjusted to compensate for thediiferent refrigerants that may be used.

The following list of typical components and values have been satisfactorily used in the embodiment of FIG. 2 of the drawings:

Transistors (ref. numerals) Thermistor sensors (ref. numerals):

53 RL21E1T (:L-5%) (Keystone Carbon Co.).

42 RLB1T (i5%) (Keystone Carbon Co.). Indicator lamps (ref. numerals):

160, 161 a. 28U filament type 1819.

162, 163 6.3U .25 amp filament type 44. Potentiometers (ref. numerals):

54 2K wirewound (Clarostat type 43Cl).

44 5K wirewound (Clarostat type 43Cl Fixed resistors (ref. numerals):

120 16.5K ohms.

121 11.8K ohms.

164 15K ohms.

165, 166, 167, 168 10K ohms.

104 35.7K ohms.

105 14.7K ohms.

169 19.1K ohms.

122 1.91K ohms.

170, 171, 172, 173, 174, 175 3.9K ohms.

176, 115, 177, 177', 178, 179 18K ohms.

180 10K ohms.

181 820K ohms.

182, 183 1.5 Megohms.

184 150 ohms.

185 2.7K ohms.

186 1.3K ohms.

187 10 ohms.

188 300 ohms. Electric valves (ref. numerals):

32, 34 22V type C2Da1251 (Skinner Electric Valve).

Pressure transducers (ref. numerals):

0-80 lbs. (Bourns Inc. Type 312).

51 0-400 lbs. (Bourns Inc. Type 312).

The control system as described provides a means of accurately obtaining the proper amounts of refrigerant charge in an operating refrigeration system with respect to its environment and regardless of whether or not the refrigerating system may be of the type using an expansion valve or a capillary tube. Rapid response of the sensors and accuracy over a wide range permits operation with a minimum Waste of refrigerant and over a wide range of operating conditions. An easy means for adjusting the control settings is provided by the manually adjustable potentiometers 44 and 54 and such adjustments can easily be made to compensate for using various refrigerant agents. The use of electrical summing circuits for responding to the different related conditions of suction line pressure and temperature, liquid line pressure, and ambient temperature together with an electrically controlled inlet valve enable the functioning of the single inlet valve to be equivalent to the function of both a blocking valve and an inlet valve as has been previously required in the manually operable charging control system described in the aforementioned copending application Serial No. 498,923.

Various modifications may be made within the spirit of the invention.

We claim as our invention:

1. Refrigerant charging apparatus adapted to be detachably connected to a source of refrigerant for predetermining the charge of refrigerant in an operating cooling system of the type containing a refrigerant and having a suction line gauge port and a liquid line gauge port comprising, an electrically controlled inlet valve having an inlet port for connection to the source of refrigerant and an outlet port for connection to the suction line gauge port, a first pressure transducer adapted to'be connected to the suction line gauge port to provide an electric signal relative to sensed pressure in the suction line, a first temperature transducer adapted to be connected to the suction line to provide an electric signal relative to sensed temperature of the suction line, a control circuit interconnecting said inlet valve and the signals from said first temperature and pressure transducers to control said inlet valve to be open for a related sensed temperature and pressure of the suction line, a second pressure transducer adapted to be connected to the liquid line gauge port to provide an electric signal relative to the sensed pressure of the liquid line, a second temperature transducer adapted to provide an electric signal relative to sensed ambient temperature, and an interlock circuit interconnecting said inlet valve and the signals from said second temperature and pressure transducers to prevent the opening of said inlet valve by said control circuit in the presence of related conditions of ambient temperature and liquid line pressure as sensed by said second temperature and pressure transducers.

2. The invention of claim 1 in which there is additionally provided an electrically controlled bleed valve adapted to be connected between the suction line gauge port and the atmosphere to bleed excess refrigerant from the suction line when the bleed valve is open, and said control circuit is connected to control said bleed valve to be open for related sensed conditions of temperature and pressure in said suction line as sensed by said first temperature and pressure transducers.

3. The invention of claim 1 in which the connections between the first temperature and pressure transducers to said control circuit include a summing circuit for the electrical signals from the transducers, said summing circuit having means to adjustably predetermine the sensed relation of temperature and pressure producing an output signal to the control circuit that is effective to cause the control circuit to control said input valve to be open.

4. The invention of claim 1 in which the connections between the second temperature and pressure transducers to said interlock circuit include a summing circuit for the electrical signals from the transducers, said summing circuit having means to adjustably predetermine the sensed relation of temperature and pressure producing an output signal to said interlock circuit that is effective to prevent said inlet valve from being opened.

5. The invention of claim 2 in which the connections between the first temperature and pressure transducers to said control circuit include a summing circuit for the electrical signals from the transducers, said summing circuit having means to adjustably predetermine the sensed relation of temperature and pressure producing an output signal to the control circuit that is effective to cause the control circuit to control said input valve to be open.

6. The invention of claim 2 in which the connections between the second temperature and pressure transducers to said interlock circuit include a summing circuit for the electrical signals from the transducers, said summing circuit having means to adjustably predetermine the sensed relation of temperature and pressure producing an output signal to said interlock circuit that is eflective to prevent said inlet valve from being opened.

7. The invention of claim 2 in which the connections between the first temperature and pressure transducers to said control circuit include a first summing circuit for the electrical signals from the transducers, said first summing circuit having means to adjustably predetermine the sensed relations of temperature and pressure producing an output signal to the control circuit that is effective to control said bleed valve to be open.

8. The invention of claim 2 in which the connections between the first temperature and pressure transducers to said control circuit include a first summing circuit for the electrical signals from the transducers, said first summing circuit having means to adjustably predetermine the sensed relation of temperature and pressure producing a first output signal to the control circuit that is effective to control said bleed valve to be open and a second output signal that is elfective to control said input valve to be open.

9. The invention of claim 8 in which said interlock circuit is effective to block the second output signal and prevent the opening of the inlet valve in the presence of related conditions of ambient temperature and liquid line pressure and at the same time said control circuit is effective to connect said first output signal to open said bleed valve in the presence of related conditions of temperature and pressure of the suction line.

References Cited UNITED STATES PATENTS 2/1950 Shoemaker 62--149 2/1967 Miller et a1. 62-149 

